Mod5 protein binds to tRNA gene complexes and affects local transcriptional silencing.

The tRNA gene-mediated (tgm) silencing of RNA polymerase II promoters is dependent on subnuclear clustering of the tRNA genes, but genetic analysis shows that the silencing requires additional mechanisms. We have identified proteins that bind tRNA gene transcription complexes and are required for tgm silencing but not required for gene clustering. One of the proteins, Mod5, is a tRNA modifying enzyme that adds an N6-isopentenyl adenosine modification at position 37 on a small number of tRNAs in the cytoplasm, although a subpopulation of Mod5 is also found in the nucleus.

Silencing near tRNA genes is nucleosome-mediated and distinct from boundary element function.

Transfer RNA (tRNA) genes and other RNA polymerase III transcription units are dispersed in high copy throughout nuclear genomes, and can antagonize RNA polymerase II transcription in their immediate chromosomal locus. Previous work in Saccharomyces cerevisiae found that this local silencing required subnuclear clustering of the tRNA genes near the nucleolus. Here we show that the silencing also requires nucleosome participation, though the nature of the nucleosome interaction appears distinct from other forms of transcriptional silencing.

Hebephilia and the construction of a fictitious diagnosis.

As mass media and the advertising industry sexualize children at earlier ages, DSM-5 is considering a proposal for a new mental disorder involving sexual attraction to adolescents. Despite the fact that most men are sexually aroused by pubescent teens, some clinicians and researchers believe they have identified a new subgroup of chronically impaired men who are compulsively drawn to older children. We discuss the proposal and conclude that it is insufficiently documented and that with such potentially serious medicolegal consequences, inclusion in the new manual is not advised.

The dual use of RNA aptamer sequences for affinity purification and localization studies of RNAs and RNA-protein complexes.

RNA affinity tags (aptamers) have emerged as useful tools for the isolation of RNAs and ribonucleoprotein complexes from cell extracts. The streptavidin binding RNA aptamer binds with high affinity and is quickly and cleanly eluted with biotin under mild conditions that retain intact complexes. We describe the use of the streptavidin binding aptamer as a tool for purification and discuss strategies towards the design and production of tagged RNAs with a focus on structured target RNAs.

Clustering of yeast tRNA genes is mediated by specific association of condensin with tRNA gene transcription complexes.

The 274 tRNA genes in Saccharomyces cerevisiae are scattered throughout the linear maps of the 16 chromosomes, but the genes are clustered at the nucleolus when compacted in the nucleus. This clustering is dependent on intact nucleolar organization and contributes to tRNA gene-mediated (tgm) silencing of RNA polymerase II transcription near tRNA genes. After examination of the localization mechanism, we find that the chromosome-condensing complex, condensin, is involved in the clustering of tRNA genes.

Silencing near tRNA genes requires nucleolar localization.

Transcription by RNA polymerase II is antagonized by the presence of a nearby tRNA gene in Saccharomyces cerevisiae. To test hypotheses concerning the mechanism of this tRNA gene-mediated (tgm) silencing, the effects of specific gene deletions were determined. The results show that the mechanism of silencing near tRNA genes is fundamentally different from other forms of transcriptional silencing in yeast.

A role for semaphorin 3A signaling in the degeneration of hippocampal neurons during Alzheimer's disease.

Among the earliest invariant neuropathological changes in Alzheimer's disease (AD) is the degeneration of vulnerable hippocampal CA1 and subicular pyramidal neurons. Semaphorin 3A (Sema3A) is a secreted protein that functions in signaling growth cone collapse, chemorepulsion and neuronal apoptosis during early development of the central nervous system. In this report we show that accumulation of an internalized form of Sema3A is associated with degeneration of neurons in vulnerable fields of the hippocampus during AD.

Nucleolar clustering of dispersed tRNA genes.

Early transfer RNA (tRNA) processing events in Saccharomyces cerevisiae are coordinated in the nucleolus, the site normally associated with ribosome biosynthesis. To test whether spatial organization of the tRNA pathway begins with nucleolar clustering of the genes, we have probed the subnuclear location of five different tRNA gene families. The results show that tRNA genes, though dispersed in the linear genome, colocalize with 5S ribosomal DNA and U14 small nucleolar RNA at the nucleolus.

TorsinA immunoreactivity in inclusion bodies in trinucleotide repeat diseases.

A mutation of the DYT1 gene, which codes for torsinA, has been identified as a cause of autosomal dominantly inherited dystonia. The function of torsinA is not yet known, but it is found throughout the central nervous system and has been identified in Lewy bodies in Parkinson's disease. We examined cases of Huntington's disease, spinocerebellar ataxia type III, and Huntington's disease-like 2 using antibodies to torsinA, and found that ubiquitinated, intranuclear neuronal inclusions were torsinA-immunoreactive, possibly indicating a role for torsinA in protein degradation.

Localized expression of small RNA inhibitors in human cells.

Several types of small RNAs have been proposed as gene expression repressors with great potential for use in gene therapy. RNA polymerase III (pol III) provides an ideal means of expressing small RNAs in cells because its normal products are small, highly structured RNAs that are found in a variety of subcellular compartments. We have designed cassettes that use human pol III promoters for the high-level expression of small RNAs in the cytoplasm, nucleoplasm, and nucleolus.

Severe generalized dystonia due to primary putaminal degeneration: case report and review of the literature.

Putaminal lesions of a variety of etiologies may cause secondary dystonia. We report on a case of primary putaminal degeneration as a cause of severe childhood-onset generalized dystonia and review the literature of the pathology of dystonia. A 44-year-old patient with severe generalized childhood-onset dystonia and macrocephaly underwent neurological evaluation and neuropathological examination.

Effective expression of small interfering RNA in human cells.

In many eukaryotes, expression of nuclear-encoded mRNA can be strongly inhibited by the presence of a double-stranded RNA (dsRNA) corresponding to exon sequences in the mRNA (refs 1,2). The use of this "RNA interference" (RNAi) in mammalian studies had lagged well behind its utility in lower animals because uninterrupted RNA duplexes longer than 30 base pairs trigger generalized cellular responses through activation of dsRNA-dependent protein kinases. Recently it was demonstrated that RNAi can be made to work in cultured human cells by introducing shorter, synthetic duplex RNAs (approximately 20 base pairs) through liposome transfection.

Brief therapy in the age of Reagapeutics.

American society is eager to embrace brief therapy as one answer to skyrocketing bills and the limited supply of mental health care providers. In the new healing philosophy of "Reagapeutics," brief therapy symbolizes our increasing sense of futurelessness in the nuclear era, our impatience in this age of haste, and our intolerance for dependency.